It is known in the art that polymethacryloyloxybenzoic acid having units of the formula: ##STR1## may be produced in the liquid crystalline state by polymerizing the monomer in p-cetyloxybenzoic acid (CBA) or in the liquid state by employing isotropic solvents such as dimethylformamide (DMF). This polymer is described as being a "comb polymer" in that it possesses mesophase forming oxybenzoate side chains depending from a methacrylate backbone. Due to the interaction of these depending sidechains, the polymer displays a smectic arrangement of macromolecules in the mesophase in certain environments. That is, the elongated molecules are found in parallel planes or layers, with the side chains linking across the plane lines.
The prior art methods for producing these polymers are disclosed in Amerik et al, "Polymerization of p-Methacryloyloxybenzoic Acid in Mesomorphic and in Liquid States", J. Poly Sci., Part C, No. 23 pp. 231-238 (1968), the content of which is incorporated by reference in the interest of brevity and clarity. As described therein, the polymer which is produced in the liquid crystalline state has a molecular weight of about 600,000 which corresponds to an intrinsic viscosity of from 0.7 to 0.8. The polymer which results from the liquid state reaction has a molecular weight of about 50,000 and an intrinsic viscosity of about 0.15 dl/g. Similar methods of producing polymethacryloyloxybenzoic are disclosed in: Blumstein et al, "Polymerization of p-Methacryloyloxy Benzoic Acid With Liquid Crystalline Media" in Liquid Crystals 3, Part II, pp. 1075-1087 (Brown & Labes, ed., Gordon & Breach Science Pub. Inc., New York, N.Y., 1971); Blumstein et al, "Crystallinity and Order in Atactic Poly (acryloyloxybenzoic acid) and Poly (methacryloyloxybenzoic acid)", Macromolecules, Vol. 9, No. 2, pp. 243-247 (March-April 1976); and Blumstein et al, "Oriented Polymer Growth in Thermotropic Mesophases", Macromolecules, Vol. 8, No. 1, pp. 73-76 (1975).
Known methods of preparing polymethacryloyloxy-benzoic acid suffer from various disadvantages. For example, the polymer produced in a dimethylformamide environment has a low molecular weight (corresponding to an intrinsic viscosity of about 0.15 dl/g when measured in a 0.1% solution of dimethylformamide at 25.degree. C.), while the polymer produced in p-cetyloxybenzoic acid is of an intermediate molecular weight (corresponding to an intrinsic viscosity of about 0.7 dl/g). When calculated as a 0.2% weight solution in 2N NaOH at 25.degree. C., the polymers have an inherent viscosity (I.V.) of less than 0.1 dl/g and 0.25 dl/g, respectively. Due to their relatively low molecular weight, the polymers of the prior art cannot be employed in the production of high strength fibers, plastics or films. In fact, in attempting to produce melt spun fibers from the low and intermediate molecular weight polymers of the prior art, it has been found that such polymers decompose before fibers can be formed.
Furthermore, because the low and intermediate molecular weight polymers exhibit a relatively low viscosity they are unsuitable as flooding agents in oil fields, which require fluids of much higher viscosity.
In addition to the aforementioned disadvantages, the prior art processes for producing polymethacryloyloxybenzoic acid employ non-aqueous solvents which present serious environmental and health hazards. Also, these non-aqueous solvents present economic difficulties in terms of both the cost of the solvent, per se, as well as the costs of solvent recovery and safety precautions. Since the non-aqueous solvents are not totally recoverable, the production cost of the polymer by either of the above-discussed prior art methods would be further increased by the continuous consumption of solvent.
In commonly assigned U.S. Ser. No. 871,280 filed concurrently herewith by Eui Won Choe, and entitled "Polyacryloylaminobenzoic acid, Polymethacryloylaminobenzoic Acid and Method of Preparation", there is described polymers which primarily differ from the polymers of the present invention by having an amino group in lieu of the oxy group. The method of preparing such polymers is also disclosed.
In commonly assigned U.S. Ser. No. 871,281 filed concurrently herewith by Eui Won Choe, Marshall Tan and Robert Mark Mininni, and entitled "Process for Producing Anisotropic Dopes and Articles thereof from Benzoic Acid Derivative Polymers", there is a described anisotropic dopes which are employed in the formation of fibers and the method of preparing the dopes.
The search has continued for high molecular weight methacryloyloxybenzoic acid polymers useful in producing melt spun fibers. This invention was made as a result of that search.
Accordingly, a general object of the present invention is to avoid or substantially alleviate the above identified problems of the prior art.
It is another object of the present invention to provide a high molecular weight polymer.
More specifically, it is an object of the present invention to provide a high molecular weight methacryloyloxybenzoic acid polymer having an inherent viscosity of at least about 1.0 dl/g.
It is another object of the present invention to provide high molecular weight methacryloyloxybenzoic acid polymer which may be formulated into high strength fibers, films and plastics and which may also be used as a flooding agent in oil fields.
Yet another object of the present invention is to provide a relatively inexpensive process for preparing a high molecular weight polymer in an aqueous medium.
Other objects and advantages of the invention will become apparent from the following summary and description of the preferred embodiments of the present invention.